Sunday, January 21, 2018

The three baggage handlers are presented along with the stolen items. Photo: Sakoo Police

Sakoo Police Chief Col Jirasak Sieamsak told The Phuket News January 21st that Sakoo Police were notified that passengers’ items had been being stolen since December last year.“A team of Sakoo Police led by Lt Col Salan Santisatsanakun together with a team of Phuket Tourist Police led by Maj Eakkachai Siri investigated the incidents and checked CCTV footage,” Col Jirasak said.“Today (January 21st) Police arrested two suspects; Nirut Saksri, 29 and Manot Nakpijit, 30 both from Phichit. Police then carried out a search of a house in Sakoo and seized several items. Police also found one more suspect; Chakrit Janprasert, 23 also from Phichit,” Col Jirasak explained.Police seized more than 100 items including laptop computers, mobile phones, whiskey, watches, sunglasses, jewelry and other items,” Col Jirasak explained.“All three suspects admitted to stealing passengers’ items while working as baggage handlers at the airport.,” Col Jirasak noted.“Nirut and Manot were charged with carrying forbidden limited items in to the kingdom by not passing the customs process and illegal possession of Category 5 drug (marijuana) while Chakrit was charged with possession of Category 1 drug (ya bah),” Col Jirasak said.“The arrests came after victim(s) reported having has items gone missing from their luggage at the airport. In the past police have randomly checked baggage staff and arrested them. Sometimes passengers did not take action against as they stole small items. Sometimes passengers were not sure where they had lost their items.“Following this incident we will increase security. In addition, we will ask baggage handlers and airport staff to join a meeting where it will be explained what will happen to tourism and what the punishments are for these kinds of criminals,” Col Jirasak added.Story and photo ➤ https://www.thephuketnews.com

FORT WORTH, Texas — Prosperity preacher Kenneth Copeland recently acquired a Gulfstream V private jet, which his staff says is “debt free” because of the donations of his followers. The announcement has drawn both applause and outrage.Copeland’s organization announced on Jan. 12 that the 81-year-old took possession of the jet, which he purchased from actor, comedian and gospel songwriter Tyler Perry.“[T]he Holy Spirit confirmed to Brother Copeland that the Gulfstream V was the plane the Lord had set aside for KCM,” claimed Charlie Bollinger, who identified as a volunteer Elite CX Team Leader. “Right away discussions began, and Brother Copeland developed a wonderful personal relationship with the seller, Christian businessman and moviemaker Tyler Perry.”“Soon a contract was signed, a cash deposit was paid, and the aircraft was brought to Dallas for a very thorough pre-buy inspection process, which [was] wrapped up in November,” he continued. “And praise God, it was actually during Thanksgiving week that the purchase was completed, the title was signed, and thanks to the CX Team, the cash was in the bank to mark it paid in full!”The Elite CX Team is a group of Copeland supporters who purpose to assist the prosperity preacher financially with his stated projects. Copeland points to a 2002 “prophecy” given by friend Keith Moore of Faith Life Church in Branson, who stated that the Lord was going to raise up wealthy supporters to back Copeland.“Thus saith the Lord: I am rallying and raising up support to you. It will far surpass all you have previously seen or known,” Moore said. “I’m joining to you new partners who are very strong financially, and they will obey Me. I’m prospering your longtime partners with supernatural increase and they will obey Me.”Copeland opined in a video posted to YouTube that he believed that the prophecy was coming to pass with the purchase of the Gulfstream V.While it is unclear as to how much was paid for the jet, Bollinger notes that another $2.5 million is desired to upgrade the avionics in light of soon-coming FAA standards, and that the ultimate goal is to raise $17 million, which will include constructing a hanger for the plane.

“[E]arlier this year when the CX leadership team met to pray and hear from the Lord, the word we heard was harvest. Yes, harvest, harvest, harvest!” he wrote. “The Lord reminded us that, through our CX Team giving, together we have sown into KCM a Citation X, a state-of-the-art HD TV truck, and now we’ve sown a Gulfstream V—all of which are producing a bountiful harvest for every single team member.”As previously reported, in 2015, Copeland asserted on his television broadcast, “The Believer’s Voice of Victory,” that he flies on a private jet to avoid being bothered by “demon” passengers.“Oral [Roberts] used to fly airlines,” he said. “But even back then it got to the place where it was agitating his spirit—people coming up to him, he had become famous, and they wanted him to pray for them and all that. You can’t manage that today [in] this dope-filled world, and get in a long tube with a bunch of demons. And it’s deadly.”

While he said that he didn’t want to fly with a “bunch of demons,” moments later, Copeland contended that he needed a private jet to help reach the lost.“We’re in soul business here. We’ve got a dying world around us. We’ve got a dying nation around us,” Copeland proclaimed. “We can’t even get there on the airlines.”Last month, in the midst of a series on “supernatural wealth transfer,” his organization posted to social media the exhortation to make the faith confessions, “The wealth of the sinner comes to me now,” “The Lord is increasing me more and more,” and “I call in the harvest on every seed sown.”The announcement of the purchase of the Gulfstream V has generated mixed reaction, with some praising God for the plane and others lamenting that the money was not used to help the poor and hungry.“My Father God is raising me to become like the Elite CX Team partners, moving His kingdom forward through prosperity. Hallelujah!” one commenter wrote.“I am so happy it is here. I know God is going to use you and the plane to bless so many people. I am praying and believing for finances for the hanger and the runway,” another stated.“Reminds me of the man who said, ‘I will pull down my barns and build bigger ones,'” a third wrote, referring to Christ’s words in Luke 12. “And, oh yes, whilst half the world goes to sleep each night with an empty stomach. Keep on your blindfolds all you gullible people who give to this scam. What a shame.”“So somehow sowing the Gospel of Christ crucified and reaping a harvest of righteousness has become sowing money into an organization and reaping a harvest of sweet vehicles for said organization and its leader?” another asked.Jesus said in Luke 12:15, “Take heed, and beware of covetousness, for a man’s life consisteth not in the abundance of the things which he possesseth.”Story, comments, video and photo ➤ http://christiannews.net

LOXAHATCHEE, Florida (CBS12) — A small experimental helicopter crashed Sunday afternoon in Royal Ascot Estates, Palm Beach County Fire Rescue said.The helicopter crashed while taking off from the owner's backyard on West Lancashire Drive, according to fire officials.The pilot, an adult man, was taken to a local hospital for treatment, fire officials said. He was the only one on board.Story and photo gallery ➤ http://cbs12.com

IOWA CITY — As World War I was coming to an end and the United States was shifting its focus on aviation from warfare to peacetime uses, Iowa City flew into the airport business with its new facility.In 1918, the Iowa City Municipal Airport opened its doors as a stop for airmail planes. Fast forward to today, and the general aviation airport is completing about 36,000 operations per year, which includes both takeoffs and landings, all while planning a centennial celebration.“Commercial aviation in Iowa was basically born here with the airmail route,” said Michael Tharp, airport operations specialist. The Midwest route for airmail would typically go from Omaha to Chicago with a stop in Iowa City, he said.Now, the airport is a general aviation facility, which Tarp said typically means any airport that doesn’t serve military or commercial airline flights.As aviation use in the country grew, the airport added passenger service, which lasted up until the 1970s, Tharp said. The airport mostly serves flights such as business charters, medical transports and crop-dusting planes.

Aircraft, a Cessna Citation (left) and a Cessna 182, occupy the newest hanger built at the Iowa City Municipal Airport in Iowa City on January 19, 2018. The airport is celebrating its 100th anniversary.

The airport is home to 92 different aircraft as well as the University of Iowa’s Operator Performance Laboratory for aviation research.“Even if you can’t see the whole aspects of aviation, there are so many ways aviation touches a community,” Tharp said. “We’re ... still serving a pretty healthy general aviation community.”As part of the 100-year anniversary celebration, airport staff are planning events for June 8-10. While the exact details are still yet to be determined, Tharp said he wanted activities that touch on the different eras in aviation history, as well as features that explain what the future of aviation could be during the next 100 years.“One hundred years, we obviously want to mark that. It’s not only important to the airport, we think it’s a pretty important event to the community,” Tharp said.Tharp said he hopes the events help to get the next generation interested in aviation. He said the already-existing Young Eagles program to give children free plane rides every year already helps do that.Tharp said that airport staff also hope to upgrade the public viewing area of the airport to a more parklike atmosphere to make it a destination for activities such as family picnics.“That’s the whole purpose, is get them at least exposed to aviation, talk a little bit about what aviation can do, how they can get more involved,” Tharp said. “It’s one of those things where if you’re not directly involved in it, sometimes it’s hard to see the benefits.”Story and slideshow ➤ http://www.thegazette.com

Location: Kilbourne, LAAccident Number: CEN16LA154Date & Time: 04/18/2016, 0910 CDTRegistration: N301LAAircraft: AIR TRACTOR INC AT 502Aircraft Damage: DestroyedDefining Event: Loss of control in flightInjuries: 1 FatalFlight Conducted Under: Part 137: Agricultural On April 18, 2016, about 0910 central daylight time, an Air Tractor Inc AT-502 airplane, N301LA, impacted terrain during spray operations near Kilbourne, Louisiana. The pilot was fatally injured, and the airplane was destroyed. The airplane was registered to and operated by Pioneer Flying Service, Inc., under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The local flight departed a private airport about 0900. According to operator personnel, the pilot was conducting his second load of spray operations for the day to the same farm area, which was about ¼ mile north of the accident site. A witness near the accident noticed the airplane enter a rapid descent while in a turn until it impacted the ground. A post-crash fire ensued.The farmer whose field was being sprayed stated the pilot was "dressing up" a field, which had a tight area shaped like a bull nose, with trees at the end. The farmer did not witness the accident. He remarked the pilot was able to spray tight areas of fields that other pilots elected not to spray. Pilot InformationCertificate: CommercialAge: 48, MaleAirplane Rating(s): Single-engine LandSeat Occupied: FrontOther Aircraft Rating(s): NoneRestraint Used: UnknownInstrument Rating(s): NoneSecond Pilot Present: NoInstructor Rating(s): NoneToxicology Performed: YesMedical Certification: Class 2 With Waivers/LimitationsLast FAA Medical Exam: 06/01/2015Occupational Pilot: YesLast Flight Review or Equivalent: 03/15/2016Flight Time: (Estimated) 13261 hours (Total, all aircraft), 2463 hours (Total, this make and model), 13261 hours (Pilot In Command, all aircraft), 100 hours (Last 90 days, all aircraft), 50 hours (Last 30 days, all aircraft), 2 hours (Last 24 hours, all aircraft)The pilot, age 48, held a commercial pilot certificate with an airplane single-engine land rating. The pilot held a second-class medical certificate issued on June 1, 2015, with the restriction that he must wear corrective lenses for near vision. The date of his last flight review was March 15, 2016. Aircraft and Owner/Operator InformationAircraft Manufacturer: AIR TRACTOR INCRegistration: N301LAModel/Series: AT 502Aircraft Category: AirplaneYear of Manufacture: 1989Amateur Built: NoAirworthiness Certificate: RestrictedSerial Number: 502-0037Landing Gear Type: TailwheelSeats: 1Date/Type of Last Inspection: 02/17/2016, AnnualCertified Max Gross Wt.: 9400 lbsTime Since Last Inspection:Engines: 1 Turbo PropAirframe Total Time: 9585 Hours at time of accidentEngine Manufacturer: Pratt and WhitneyELT: Not installedEngine Model/Series: PT6A-34GRegistered Owner: Pioneer Flying ServiceRated Power: 750 hpOperator: PIONEER FLYING SERVICE INCOperating Certificate(s) Held: Agricultural Aircraft (137)Operator Does Business As:Operator Designator Code: JQBG The single-engine low-wing conventional-geared airplane was equipped with a Pratt and Whitney PT6A-34AG turbo-prop engine. According to the operator, the last annual inspection was performed on February 17, 2016. The airframe total time was 9,585 hours and the engine total time was 7,022 hours, with 445 hours since the last hot section inspection. Meteorological Information and Flight PlanConditions at Accident Site: Visual ConditionsCondition of Light: DayObservation Facility, Elevation: KBQP, 167 ft mslObservation Time: 0915 CDTDistance from Accident Site: 32 Nautical MilesDirection from Accident Site: 243°Lowest Cloud Condition: ClearTemperature/Dew Point: 19°C / 15°CLowest Ceiling: NoneVisibility: 10 MilesWind Speed/Gusts, Direction: 4 knots, 80°Visibility (RVR):Altimeter Setting: 30.24 inches HgVisibility (RVV):Precipitation and Obscuration: No Obscuration; No PrecipitationDeparture Point: Pioneer, LA (PRI)Type of Flight Plan Filed: NoneDestination: Pioneer, LA (PRI)Type of Clearance: NoneDeparture Time: 0900 CDTType of Airspace: Class GAt 0915, the weather observation station at Morehouse Memorial Airport (BQP), Bastrop, Louisiana, located about 32 miles southwest of the accident site, reported the following conditions: wind 080 degrees at 4 knots, 10 miles visibility, clear skies, temperature 19°C, dew point 15°C, altimeter setting 30.24 inches of mercury.

Wreckage and Impact InformationCrew Injuries: 1 FatalAircraft Damage: DestroyedPassenger Injuries: N/AAircraft Fire: On-GroundGround Injuries: N/AAircraft Explosion: NoneTotal Injuries: 1 FatalLatitude, Longitude: 32.999722, -91.315000 The airplane impacted a soft open field. Other than a set of electrical lines, no obstacles were in the immediate area of the wreckage. The wreckage had no signs of an in-flight impact with wires, trees, or other obstacles. The wooded area toward the sprayed field was searched for broken branches or other signs of tree impact, with none observed. The wreckage was confined to the immediate vicinity of the impact site. The impact crater contained pieces of engine cowling, windshield plexiglass, and the hopper top and lid. The engine penetrated about 3 ft deep into the soft soil. Radiating from the crater were impressions in the soil, consistent with impact marks from the leading edge of both wings. The wings were located about 10 feet away from these impressions. Both wings were crushed aft, with the left wing receiving more damage than the right wing. The aft fuselage and rudder showed signs of momentum toward the left side of the airplane. The ground impact markings and wreckage were consistent with a steep, nose down impact at low groundspeed. The fuselage was mostly destroyed by impact forces and a post-crash fire.All control surfaces were located and identified, except for the vertical stabilizer. The only piece of the vertical stabilizer that was located was a short piece of the stabilizer rear spar that remained attached to the lower portion of the rudder. The lower hinge point of the rudder was found fully intact with minimal damage. The end of the wire deflector cable that was attached to the top of the stabilizer was found underneath the cockpit wreckage. Multiple pieces of fire-damaged aluminum were identified as possible vertical stabilizer components, but none could be confirmed. A witness mark was observed on the top fuselage skin that corresponded to the shape of the vertical stabilizer's leading edge.The wings flaps were in the full up position. Flight control continuity was confirmed to the extent possible, with several components consumed by the fire or cut by emergency response personnel during the pilot's extrication. The aileron/rudder interconnect system, which is a system of cables that connect the rudder pedals to the aileron controls to assist the pilot with coordinated flight, had been removed from the airplane.The engine was damaged by the post-crash fire, with the inlet case fractured, causing complete separation of the accessories gearbox from the engine. Rotational signatures were observed throughout the compressor and power turbines and adjacent static components, consistent with the engine rotating under power during impact. There was no evidence of pre-impact anomalies of the engine, airframe, or propeller.Due to fire damage, data from a GPS unit found in the wreckage could not be downloaded. Medical And Pathological InformationDuring his last FAA medical examination, the pilot reported heterophoria (cross-eyes), previous treatment for a kidney stone, and long-standing hypertension. He also reported using nisoldipine, valsartan, and hydrochlorothiazide, commonly sold with the names Sular and Diovan-HCT. Used to treat his blood pressure, none of these medications are generally considered impairing.According to the autopsy report from the West Carroll Parish Coroner's Office in Oak Grove, Louisiana, the cause of death was multiple blunt force injuries and the manner of death was accident. The heart weighed 550 grams and was enlarged due to concentric left ventricular hypertrophy (LVH). The left wall of the ventricle was reported as 1.8 cm thick; measurements in other areas were not reported. Average for a man with the pilot's weight of 282 pounds is 443 grams with a range of 335-584 grams; average left ventricular wall thickness is about 1.3 cm. LVH is commonly caused by longstanding hypertension. Toxicology performed by the FAA's Bioaeronautical Sciences Research Laboratory identified valsartan in urine and cavity blood. Valsartan is described above.NTSB Identification: CEN16LA15414 CFR Part 137: AgriculturalAccident occurred Monday, April 18, 2016 in Kilbourne, LAAircraft: AIR TRACTOR INC AT 502, registration: N301LAInjuries: 1 Fatal.This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.On April 18, 2016, about 0910 central daylight time, an Air Tractor Inc. AT-502 airplane, N301LA, was destroyed after impact with terrain near Kilbourne, Louisiana. The pilot was fatally injured. The airplane was registered to and operated by Pioneer Flying Service Inc. under the provisions of 14 Code of Federal Regulations Part 137 as an aerial spraying flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The local flight departed a private airport about 0900.According to operator personnel, the pilot was conducting his second load of spray operations to the same farm area. A witness located near this farm stated she noticed the airplane in a turn and subsequently enter into a rapid descent until impacting the ground. The Federal Aviation Administration inspector responding to the accident site reported the airplane impacted into an open field with a steep nose down attitude.At 0915, the weather observation station at Morehouse Memorial Airport (BQP), Bastrop, Louisiana, located about 32 miles southwest of the accident site, reported the following conditions: wind 080 degrees at 4 knots, 10 miles visibility, clear skies, temperature 19 degrees C, dew point 15 degrees C, altimeter setting 30.24 inches of mercury.

Some of the 40 employees in Singapore let go by luxury jet operator Zetta Jet after its sudden closure say they are still owed expenses and paid leave.The company was incorporated here in 2015 and had offices in the United States.It was ordered by a US court to stop operating on November 30 last year despite an attempt to rescue it financially and keep operations going.Zetta Jet ran into trouble when its US and Singapore-based shareholders were embroiled in a legal tussle after the company filed for Chapter 11 bankruptcy protection in the US in mid-September last year.Singapore-based staff of Zetta Jet, who included pilots and cabin crew and those in finance, sales and operations, had followed the unfolding events closely.An operations employee told The Straits Times: "Some of us were concerned when we started hearing rumors in August. But we were assured that all would be fine."Another employee said: "There were also issues with Zetta Jet (corporate) credit cards in the final months. So, many of the crew used their personal (credit) cards to keep things working."It includes paying for Uber rides with their personal cards instead of the corporate cards.In mid-November, staff in the US and Singapore received a letter via e-mail from Zetta Jet's US shareholders, Mr. James Seagrim and Mr. Matthew Walter.They said that they were shocked and disappointed by a US Court's refusal to sanction an investment proposal by Scout Aviation, which had agreed to pump in up to US$8.5 million (S$11.2 million) in financing.Signed by both US shareholders, the email stated that both Mr. Seagrim and Mr. Walter had no idea why the financing package was not approved."Unfortunately, due to the company's limited liquidity, we will only be able to pay salary through November 30, 2017."Prior to the Chapter 11 filing, Zetta Jet had accused its former managing director, Mr. Geoffery Cassidy, of fraud.The company lodged a lawsuit in the US against the Australia-born Mr. Cassidy, alleging that it was forced to restructure its debts because Mr. Cassidy had misappropriated funds from the company, among other claims.It also alleged that Mr. Cassidy had "wrongfully deprived Zetta Jet and/or Zetta Jet USA Inc of at least US$20 million to US$30 million".Mr. Cassidy, who was based in Singapore and removed as director in August last year, denied the allegations and secured an injunction in Singapore to stop the Chapter 11 move but the US court did not recognize it.In a November 16 letter to employees, Mr. Cassidy refuted Zetta Jet's accusations of fraud, corruption and unauthorized use of company jets.While the final chapter of the Zetta Jet saga has yet to be written due to pending lawsuits, a plan to hire former employees may have already been hatched.A private jet operator with Singapore-based US directors is believed to be recruiting former Zetta Jet employees.It is understood that the company has a fleet of seven to nine aircraft.Original article can be found here ➤ http://www.straitstimes.com

Location: Kennett, MOAccident Number: CEN16LA260Date & Time: 07/07/2016, 0650 CDTRegistration: N967JBAircraft: AIR TRACTOR INC AT-602Aircraft Damage: DestroyedDefining Event: Loss of control in flightInjuries: 1 FatalFlight Conducted Under: Part 137: AgriculturalOn July 7, 2016, at 0650 central daylight time, an Air Tractor Inc AT-602, N967JB, collided with power lines and terrain during an aerial application of a field about 4 miles northeast of Kennett, Missouri. The airplane was destroyed by impact forces. The commercial pilot sustained fatal injuries. The airplane was registered to and operated by Bootheel Air Services LLC under 14 Code of Federal Regulations Part 137 as an aerial application flight that was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight last departed from Hornersville Memorial Airport (37M), Hornersville, Missouri, about 0541.According to a Federal Aviation Administration (FAA) inspector, a chemical loader stated that the airplane was loaded at 37M with 375 gallons of liquid chemical applicant to spray a 75-acre corn crop field, which was adjacent to a bean field. There were no witnesses to the accident.The accident site was located near electrical lines that were oriented in an east/west direction and in the middle of the corn field that was being sprayed by the airplane. Two of the electrical lines were severed and a third damaged near the east edge of the field. A section of the airplane spray boom was bent around and hanging from the damaged, third electrical line. There was a ground scar consistent with the airplane's impact with terrain approximately 1,000 feet from the severed/damaged electrical line and in the bean field adjacent to the corn field. Approximately 50 feet from the severed/damaged lines, there were sections of right wing and aileron on the ground. The ground scar extended in the bean field and inn a northerly direction for approximately 200 feet. There were several propeller strikes in the ground near the beginning of the wreckage path.The propeller blades, propeller hub, engine, and landing gear were found separated from the airplane. The fuselage, remaining wing, and empennage were located near the end of the wreckage path. The cockpit and tail section had an approximate tail-to-nose heading oriented towards the south.Examination of the flight control confirmed flight control continuity. The engine turbine blades display signatures consistent with engine power. Fuel quantity could not be verified, but a fuel spill was noted underneath the wing section. There was no evidence of remaining spray chemical solution on scene. The shoulder harness air bag restraint system was deployed.The 48-year-old pilot had reported multiple orthopedic surgeries and use of medication for high cholesterol to the FAA. At the time of his last aviation medical examination, diabetes was diagnosed and treatment with metformin initiated. The aviation medical examiner questioned records from a recent hospitalization that stated the pilot had anxiety/depression but was told this was not a current diagnosis and that he had not been on medication in years. According to the autopsy performed by Mineral Area Pathology LLC, the cause of death was multiple blunt force injuries and the manner of death was accident. No significant natural disease was identified. Toxicology testing identified acetaminophen, chlorpheniramine, citalopram and its metabolite n-desmethylcitalopram, dextromethorphan and its metabolite dextrorphan in liver. Acetaminophen and chlorpheniramine were found in cavity blood and the rest were found in muscle. Acetaminophen was identified in urine.Acetaminophen is an analgesic and fever reducer available over the counter in many products; it is commonly marketed as Tylenol. Chlorpheniramine is a sedating antihistamine available over the counter in many cold, cough, and allergy preparations. It carries this warning, "May impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)."Citalopram is a prescription antidepressant medication often marketed with the name Celexa. It carries this warning, "In studies in normal volunteers, citalopram in doses of 40 mg/day did not produce impairment of intellectual function or psychomotor performance. Because any psychoactive drug may impair judgment, thinking, or motor skills, however, patients should be cautioned about operating hazardous machinery, including automobiles, until they are reasonably certain that citalopram therapy does not affect their ability to engage in such activities." N-desmethylcitalopram is its primary metabolite.Major depression itself is associated with significant cognitive degradation, particularly in executive functioning. The cognitive impairment often resolves as the emotional symptoms resolve. The FAA requires that pilots treated for depression undergo specific testing to ensure their cognitive functioning is intact and they are using a non-impairing antidepressant. The FAA's Guide for Aviation Medical Examiners states "The use of a psychotropic drug is disqualifying for aeromedical certification purposes – this includes all antidepressant drugs, including selective serotonin reuptake inhibitors (SSRIs). However, the FAA has determined that airmen requesting first, second, or third class medical certificates while being treated with one of four specific SSRIs may be considered. The Authorization decision is made on a case by case basis. The Examiner may not issue." The four potentially allowable antidepressants are fluoxetine (Prozac), escitalopram (Lexapro), sertraline (Zoloft), and citalopram (Celexa).Dextromethorphan is a cough suppressant available over the counter in many products. At usual dosing, it is not considered impairing. Dextrorphan is its primary metabolite.

NTSB Identification: CEN16LA26014 CFR Part 137: AgriculturalAccident occurred Thursday, July 07, 2016 in Kennett, MOAircraft: AIR TRACTOR INC AT-602, registration: N967JBInjuries: 1 Fatal.This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.On July 7, 2016, at 0650 central daylight time, an Air Tractor Inc AT-602, N967JB, collided with power lines and terrain during an aerial application of a field about 4 miles northeast of Kennett, Missouri. The airplane was destroyed by impact forces. The commercial pilot sustained fatal injuries. The airplane was registered to and operated by Bootheel Air Services LLC under 14 Code of Federal Regulations Part 137 as an aerial application flight that was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight last departed from Kennett, Missouri at time unknown.

With a clipboard on a leg, Lis Hendrickson pilots a Cirrus SR22 with the plane’s sidestick controller.

Lis Hendrickson has two hangars and an airstrip at her home.She also has three planes: a Cessna 170, a Cessna 120 and a Piper Super Cub. (The latter has floats and skis on the wheels right now, she said.)Hendrickson is chief flight instructor and operations director of Fly Duluth / Duluth Flying Club, a privately owned pilot training center. Before that, she wore other hats: chief flight instructor at Lake Superior College, a corporate pilot for Cirrus, flight instructor at Cloquet Airport.When she's not teaching, she's working with the Federal Aviation Administration, writing flight lessons, ensuring their planes are up on their maintenance and communicating with students.And she tries to fly as often as possible — but it wasn't always like that.

Lis Hendrickson walks around a Cirrus SR22 after a recent flight.

"I started learning how to fly when I was 30," said the 60-year-old. Before that, Hendrickson was in restaurant management. When her daughter was old enough, she decided to chase her childhood dream.She earned her pilot license in three months, she said, explaining, "A year is a normal time span."Flying is not just manipulating the controls. Ground training covers the basic systems in an airplane; you also have to learn how to fly in different weather patterns, the language of the airports and how to navigate with GPS."When I first started, I couldn't do anything but fly the airplane," she said. Your brain is so full of information, it's tough to multitask, and getting comfortable communicating with air traffic controllers takes a while. She recalled a time her flight instructor told her to announce she was making a maneuver into the headset. "I look over at him and I say, 'I can't, I'm turning,'" she said with a laugh.Hendrickson uses her experiences with her students and the instructors she oversees, and she models her teaching style after Bill Amorde at the Superior Airport."He's still the person that I look up to and try to emulate," she said. He's a designated pilot examiner, he has so much experience in many different kinds of airplanes, and he'll give real-world experience that nurtures confidence."When I'm with a student or we're on a stage check, they'll look at me and they'll say, 'Is this right?' And instead of answering their direct question, what I will say is, 'Does this sound right to you? Do you think that you're ready to take off?'" This teaches them how to be a pilot in command, and that calm step-by-step thought process will save your life, she said.

A large motivator to teach is to give back to aviation, she said, and a bonus is watching a person move from zero hours in the sky to hitting what she calls an epiphany about flying. "It feeds my soul," she said.Christy Newcomb is a customer service representative at Monaco Air Duluth, where she works with Hendrickson. Since childhood, Newcomb was drawn to flying. "This isn't something I wanted to do for a career. It's something just for me," she said by email.Newcomb earned a private pilot license with Hendrickson as her ground school and flight instructor. During her first solo flight, the two were practicing landings, when Hendrickson told Newcomb to pull in to a near control tower base."She rummaged around in the back seat of the aircraft, then opened the door (with the aircraft still running) hopped out and said, 'Go do three more.' She closed the door and walked away."It's in that moment you wonder if you're truly capable of doing these landings on your own. After you make those landings ... it's a huge boost to your self-esteem."

Lis Hendrickson checks a sample of fuel from a Cirrus SR22 to ensure that it’s clear of water. The precaution is part of a preflight inspection.

Melissa Lange has known Hendrickson since she was a flight instructor at Lake Superior College. Today, with Hendrickson as her boss, Lange also works as an instructor, and the two share the same passion for teaching.Guiding someone who has never been in or flown a plane to their first solo flight, that's at the heart of what Lange does, she said. "From takeoff to landing, it's exciting," she said.And for Hendrickson, flight instruction is a family affair.It was her father, Nils Grover, who instilled a love of flying in her. As a kid, he'd take her to the Duluth or Superior airport, where they'd watch the planes. Decades later, Hendrickson became his teacher. "He was proud to tell everybody that 'My daughter is my flight instructor.'"Teaching her father was easy; he learned quickly because he loved it. He also did a lot of self-study and practicing on flight simulators."We think alike," Hendrickson said. "We were so close that we were able to finish each other's sentences, and we were thinking the same ways."

Nils Grover

When he got sick last year, Hendrickson said she had to quit work completely to take care of him. "In one month, he was gone," she said. But the family connection lives on for Hendrickson, who flies to visit her daughter and two grandchildren in Eau Claire, sometimes only for a lunch. (The flight is 40 minutes.) She also started to teach her granddaughter the aircraft ropes when she was 6.Being in the business for this long, Hendrickson has seen many changes in plane navigation and autopilot capabilities."What hasn't changed is ... people are not expecting a woman pilot," she said. "I grew up in the '60s and '70s; it just doesn't bother me."One challenge in the field is that fewer people are flying. Earning a pilot certificate takes a lot of commitment, time, effort and money, she said. "I think that's why people think flying is for rich people. It's not ... it's $200 an hour. If that's all you do, it's fine. If you want to go hunting, fishing, snowmobiling or sailing, of course, you can't do it."Flying brings a new outlook, she said."Other little things down on the ground, don't matter because you're up in the air, and you could make a life-or-death decision. It's a huge, life-changing perspective," she said.Story and photo gallery ➤ http://www.duluthnewstribune.com

Majs. Erik Boyce and Jason Grogan died in the July 6, 2016 crash, according to officials at Marine Corps Forces Reserve. Both men flew AH-1W Super Cobras in the Marine Corps. Boyce deployed in support of operations in Iraq five times. Grogan deployed in support of Iraq operations twice and to Afghanistan once. On July 6, 2016 they were flying a Bell 525 Relentless helicopter, which went down south of Dallas in Ellis County, Texas.

Jason Grogan

Bell Helicopter pilot Jason Grogan in an undated family photo stands in front of a Bell 47G helicopter. Grogan was one of two Bell test pilots killed on July 6, 2016, when a Bell 525 crashed in southern Ellis County, Texas.

Location: Italy, TXAccident Number: DCA16FA199Date & Time: 07/06/2016, 1148 CDTRegistration: N525TAAircraft: BELL 525Aircraft Damage: DestroyedDefining Event: Aircraft structural failureInjuries: 2 FatalFlight Conducted Under: Part 91: General Aviation - Flight TestAnalysis The experimental research and development helicopter was undergoing developmental flight tests before type certification. On the day of the accident, the helicopter test crew was performing a series of one-engine-inoperative (OEI) tests at increasing airspeeds with a heavy, forward center-of-gravity configuration. (For the OEI tests, the pilots used OEI special training mode software to reduce the power of both engines to a level that simulated the loss of one engine.) The crew initiated the final planned OEI test at a speed of 185 knots. After the crew engaged OEI special training mode, rotor rotation speed (Nr) decayed from 100% to about 91%, and the crew began lowering the collective to stop Nr decay and increase Nr to 103% (the target Nr for recovery). About 5.5 seconds into the test, the crew stopped lowering the collective, and Nr only recovered to about 92%. About 6 to 7 seconds into the test, the helicopter began vibrating at a frequency of 6 hertz (Hz). The vibration was evident in both rotor systems, the airframe, the pilot seats, and the control inputs; the vertical vibration amplitude at the pilot seat peaked about 3 G. (G is a unit of measurement of acceleration; 1 G is equivalent to the acceleration caused by the earth's gravity [about 32.2 ft/sec2].) Nr remained between about 90% and 92% until about 12 to 13 seconds into the test, then began fluctuating consistent with collective control inputs; subsequent collective control input increases led to further decay in Nr. Nr decayed to about 80% as the collective was raised, and the main rotor blades began to flap out of plane. About 21 seconds into the test, the main rotor blades flapped low enough to impact the tail boom, severing it and causing the in-flight breakup of the helicopter.The main rotor, tail rotor, flight controls, powerplants, and rotor drive systems exhibited no evidence of preexisting malfunction before the vibrations began. The structural wreckage did not exhibit evidence that the oscillations themselves resulted in a structural failure leading to the in-flight breakup. Examination of the wreckage revealed no indications that the helicopter had been improperly maintained.Helicopter Performance After Stop in Nr RecoveryDuring previous OEI tests, the crew lowered the collective input to near or below 50% to allow Nr to recover. As airspeed increased during each test, the crew took longer to recover Nr to 103%. (At 102 knots, recovery time was 3.4 seconds, and at 175 knots, recovery time was 13 seconds.) However, after initiating the final OEI test at 185 knots, the crew only lowered the collective to 58% and subsequently only recovered Nr to 92%. While at 92%, the main rotor scissors mode was excited. (The main rotor scissors mode occurs when the lead-lag motions of the blades act in such a way that adjacent blades move together and apart in a scissoring motion. See the factual report for more information about the scissors mode.) The main rotor scissors mode excitation resulted in the 6-Hz airframe vertical vibration, which was transmitted to the crew seats and created a biomechanical feedback loop through the pilot-held collective control. A second feedback system, driven by the attitude and heading reference system (AHRS) inputs to the main rotor swashplate, also continued to drive the scissors mode and its resultant 6-Hz airframe vibration.Biomechanical FeedbackBiomechanical feedback in the aircraft design industry refers to unintentional control inputs resulting from involuntary pilot limb motions caused by vehicle accelerations. The gain between the vertical acceleration and 6-Hz collective stick movement can be calculated by dividing stick movement by vertical acceleration. (If no biomechanical feedback existed, there would be no gain [0 inch per G].) During the accident, the collective stick moved, on average, 0.2 inch per every G of seat acceleration. The "nonzero" relationship between the control stick amplitude and the seat vibration illustrates that biomechanical feedback contributed to the helicopter's vibration. Further, a positive value of pilot gain occurred near 6 Hz, which indicates instability in the system (meaning that any input to the system will amplify as opposed to dampen). Thus, biomechanical feedback contributed to increases in vibration amplitude during this accident.Although the helicopter manufacturer's design process for biomechanical feedback included software filters in the cyclic control laws to reduce certain types of oscillatory cyclic control inputs by the pilot, no filter was designed for the collective. Thus, the 6-Hz oscillatory collective inputs by the pilot were not filtered. As a result, a control feedback loop began when the pilot-held collective stick commanded an oscillatory collective pitch input (about 6 Hz) into the main rotor, increasing the 6-Hz vibration, which in turn increased the magnitude of the oscillatory (6-Hz) collective pitch input.In addition, the gain between the pilot movement and the collective control stick movement in the vertical axis was never tested on a shake table before the accident. For the cyclic control, lateral vibration was introduced on a shake table. This test was conducted specifically for the helicopter model's side-stick cyclic since the manufacturer expected a different transfer function from that of a traditional cyclic. For the collective control, no such test was conducted despite this being the first helicopter with a side-stick collective control. While it is possible that the decision to not shake test in the vertical axis to inform the pilot model could have been influenced by schedule pressure, interviews did not suggest that decisions would have been different given the lack of anticipation of scissors mode and resulting aerodynamic effect.Attitude and Heading Reference SystemThe AHRS is designed to detect uncommanded accelerations (such as the helicopter's reaction to a gust of wind) and reduce their effects by automatically providing corrective inputs to the main rotor swashplate. The AHRS detected and responded to the 6-Hz airframe vertical vibration in a manner that sustained the main rotor scissors mode and its resultant 6-Hz vibration. Specifically, analysis of the telemetry data revealed that the AHRS responded to the 6-Hz vibration with inputs to the main rotor swashplate analogous to a "cyclic stir" (when the cyclic control stick is moved in a stirring motion). The helicopter manufacturer's assessment of the AHRS-induced cyclic stir swashplate motion was that it would exacerbate the main rotor scissors mode. The AHRS is intended to respond primarily to lower-frequency uncommanded accelerations. Because the helicopter manufacturer did not predict an excitement of the scissors mode in the accident test flight conditions, the filter design of the AHRS allowed it to respond to the 6-Hz airframe vibration. Thus, the AHRS detected and attempted to attenuate the 6-Hz airframe vertical vibration, but its response instead exacerbated the main rotor scissors mode and its resultant 6-Hz vibration, closing the AHRS feedback loop.Reasons for Crew Stop in Nr RecoveryInvestigators explored possible reasons why the crewmembers stopped their recovery from the initial Nr droop, including a reaction to an abnormal condition on the helicopter, distraction from the recovery task, or a conservative response due to the high airspeed. Telemetry data does not indicate the existence of an abnormal condition when the crewmembers stopped their recovery. In addition, the chase helicopter crewmembers reported seeing no distractions or abnormalities outside of the helicopter (for example, birds).Therefore, investigators focused on the crew's increasingly conservative response as the airspeed increased during the tests. During the previous OEI tests, as airspeed increased, the crew recoveries took more time to reach 103% Nr and collective response became less pronounced. During postaccident interviews, helicopter manufacturer test pilots indicated that they interpreted this trend as the tendency of the crew to be more judicious while applying collective at successively higher airspeeds to avoid recovering too fast and overspeeding the rotor or damaging the transmission. Thus, the crew may have been more conservative during recovery at the helicopter's high speed during the final test. The chief test pilot also stated that if Nr had stabilized, the pilot would not have been in a rush and was possibly initiating a slow recovery.As an experimental research and development helicopter configured to carry two pilots and with no passenger seating, the accident helicopter was not required to be equipped with either a flight data recorder (FDR) or cockpit voice recorder (CVR) under the provisions of 14 Code of Federal Regulations (CFR) 91.609. (When certified as a transport-category rotorcraft under 14 CFR Part 29, the helicopter model will be equipped with both CVR and FDR recording capabilities.) A combination CVR and FDR (CVFDR) was installed in the flight test helicopter but was not operational at the time of the accident. Although investigators were able to examine and analyze telemetry data, a properly functioning CVFDR would have recorded any discussions between the accident pilots that could have offered more information about potential abnormal conditions, distractions, or reasons for their stop in recovery after initiation of the OEI test. Additionally, cockpit image recording capability would have recorded any pilot actions and interactions with the aircraft systems including avionics button presses, warning acknowledgements, and any other physical response to the aircraft. Cockpit audio and imagery could have provided insight into when the crewmembers first felt or detected the 6-Hz vibration, how they may have verbalized their assessment of an observed anomaly, and whether they attempted any specific corrective action because of the vibration. Thus, the lack of cockpit audio or image data precluded access to data needed to fully determine why the crew may have momentarily stopped the collective pitch reduction to recover Nr and any corrective actions the crew may have attempted as a result of the 6-Hz vibration.Regardless of why the crew stopped recovery of Nr at 92%, other helicopter test pilots suggested in postaccident interviews that continuous flight in the 92% to 93% Nr range was not abnormal for an OEI maneuver (in this model helicopter and another model in the helicopter manufacturer's test program). This is further supported by another model in the helicopter manufacturer's test program during which extended flight occurred in the low 90% Nr range. (The other helicopter model did not encounter any unusual behavior [rotor mode/vibration] during the test points with the extended recovery time, and the pilots did not receive negative feedback on the recovery time.) The lack of any negative feedback on extended flight in the low 90% Nr range may have reinforced that flight through that range was appropriate. On the pilot displays (specifically, the power situation indicator [PSI]) in the accident helicopter model, 90% to 100% Nr is depicted as a green range or arc. The decision to fly continuously in the 92% to 93% Nr range is consistent with typical pilot association of green arcs with flight regimes that are appropriate for continuous flight. The company's flight technology specialist stated that the colors (green arc) presented on the PSI were a precedent taken from the other helicopter model test program, which suggests that it was likely not reevaluated for appropriateness given the accident helicopter's operating limitations. In addition, flight testing was only conducted for continuous flight at 103% and 100% Nr with all engines operative; however, no testing of Nr continuously between 90% to 100% while in an OEI condition was conducted. Extended flight in the low 90% Nr range during previous testing of another helicopter model and the depiction of 90% to 100% Nr in a green arc on the PSI may have contributed to the pilots' decision to stop in the 92% range during the recovery from the OEI maneuver, which resulted in the onset and increase of the 6-Hz vibration.Crew Response to Low Nr and VibrationInterviews with the helicopter manufacturer test pilots and engineers suggest that there were two ways for the pilots to exit the low Nr and, correspondingly, the vibration condition: (1) lower/reduce the collective to increase Nr or (2) exit OEI training mode, which would increase power available from the engines. About 1.5 to 2 seconds passed between the stop at 58% collective and the onset of the vibration. Had the pilots recovered Nr to 100%, it is possible that the main rotor scissors mode would have subsided and the airframe vibrations would have dampened.Lowering the CollectiveOne option for recovering from the low Nr and vibration condition was to lower the collective to increase Nr. The investigation could not determine if the pilots' fluctuating collective inputs were deliberate when the 6-Hz vibration was dominant. Because the crew needed to be aware of low Nr to respond appropriately, investigators considered the available visual, aural, and tactile cues regarding Nr in the vibration environment.The visual cues available to the crew included the crew alerting system (CAS) text "ROTOR RPM LO," PSI numeric display, warning flag, warning push button annunciator (PBA), and the change of the PSI Nr display from a bar to an arc. The CAS text, warning flag, and warning PBA would have been flashing until acknowledged by the crew. Because the telemetry did not record crew button presses, it is not possible to know if the crew acknowledged these alerts. Studies indicate that visual acuity is negatively affected by vertical vibration, particularly in the 5- to 7-Hz frequency range (Lewis and Griffin 1980a; Lewis and Griffin 1980b). Results indicated that reading speed and accuracy degraded for amplitudes as low as 0.1 G (McLeod and Griffin 1989; Griffin and Hayward 1994). Further studies show that visual performance decreases with increasing vibration amplitude (Shoenberger 1972; Griffin 1975; Griffin 2012).The vertical vibration amplitude at the pilot seat rose above 1 G from 10 seconds into the test until the end of the test, with peaks as high as about 3 G. Given the sensitivity of the human body to vibration frequencies near 6 Hz and the extreme amplitude of the vibration environment, the displays were likely unreadable to the crew (although the colors of the warning text, flag, and PBA may have been discernable). In addition, the change of the Nr display on the PSI from bar to arc may have been recognizable; however, reading of the needle would likely not have been possible in the vibration environment. Thus, the crew was likely unable to read visual information that provided specific low Nr information, although they may have had a generalized cue that Nr was low.Aural cues available to the crew regarding low Nr included the master warning annunciation and the sound of decreasing Nr. The master warning aural tone would have annunciated at 12.5 seconds and 16.8 seconds (continuing until acknowledged by the crew). However, this tone was associated with at least 21 other warning messages and was not unique to the "ROTOR RPM LO" message despite a technical standard that requires that low Nr have a unique tone associated with it. The master aural tone annunciating continuously was chosen for test flight because audio files had not yet been developed; the helicopter manufacturer pilots and test team had decided that some aural annunciation of low Nr would be enough to proceed with test flights but that the distinct tone for low Nr was not immediately needed for flight test.Aural cues can be used for redundancy if visual information is unavailable. The accident pilots were aware that a unique tone did not exist for low Nr; however, they likely were not able to retrieve unambiguous visual information to confirm the warning, outside of a change in shape of the rpm display. Had a unique aural warning tone been implemented in the helicopter, it could have provided a salient, unambiguous cue to the crewmembers that Nr was low.Regarding the sound of decreasing Nr, under normal conditions, pilots can hear the decrease in Nr and would likely be able to tell the difference between 100% and 92% Nr. However, according to a postaccident statement by the helicopter manufacturer lead test pilot, it is uncertain whether the pilots would have heard the low Nr given the vibration environment during the accident flight.The exceedance of engine limits, which can indirectly indicate low Nr, triggers tactile cues in the pilots' collective control. Increased friction on the collective would have been present 7 to 9 seconds into the test and after 11 seconds into the test; however, it is questionable whether the crew would have noticed this increase in friction given the extreme vibration environment.In summary, although visual and aural warning cues were available to the crew during the event, unambiguous cues for low Nr were most likely unavailable visually because of the vibration and audibly because of a design decision regarding the test environment. Without an unambiguous cue for low Nr, it was unlikely that the pilots had properly distinguishable awareness of the low Nr condition for them to appropriately respond.Exiting OEI Training ModeAccording to the telemetry data, the crew did not exit OEI training mode; the engines continued producing power at a level consistent with OEI training mode remaining active until the in-flight breakup. The production version of OEI training mode software, originally created by the engine manufacturer, was modified by the helicopter manufacturer to eliminate a safeguard that automatically exited the OEI training mode when Nr fell below 90%. According to the helicopter manufacturer, automatic disengagement at 90% Nr is not low enough to allow development and demonstration of OEI recovery across the flight envelope during testing, and a lower Nr value for automatic disengagement was deemed unnecessary due to the highly controlled test environment. Thus, the crew would have had to manually exit OEI training mode. Had there been an automated safeguard to exit OEI training mode at a certain Nr threshold, it is possible that the return of full dual-engine power would have compensated for the higher power demanded by increasing collective stick inputs and returned Nr to normal levels. Investigators considered several reasons why the crew did not manually exit OEI training mode.First, investigators considered if the crew attempted to exit OEI training mode but was unable to do so due to physical limitations of the hardware. However, postaccident shake tests suggest that the display and touch functionality of the Garmin Touch Control (GTC) panel, which controlled the OEI training mode, remained intact during the vibration profile. Thus, it is unlikely that physical limitations of the hardware itself prevented the crew from exiting OEI training mode.Second, investigators considered if the crew attempted to exit OEI training mode but was unable to do so due to manual hand tracking and vibration influences. There are three ways to manually exit OEI training mode: pressing the engine fail button on the GTC OEI training page (which would be displayed on the GTC during the test), exiting the OEI training page on the GTC (using the BACK button), or moving the COSIF (crank, off, start, idle, fly) switch to any other position than "Fly." Research suggests that performance degrades in the presence of vibration and is particularly poor in the 6-Hz range as limb motion can be greater than input amplitudes at that frequency (Moseley and Griffin 1986; Collins 1973; Griffin and Hayward 1994; McLeod and Griffin 1986; Crossland and Lloyd 1993; Holcombe and Holcombe 1997; Wertheim et. al. 1995). Limb motion is also more complex given the coupled dynamics of the human body where acceleration in a single axis could result in limb motion in all six axes (McLeod and Griffin 1986; Griffin 2012; Paddan and Griffin 1988). The extreme amplitudes of the vibration could have prevented the pilots from successfully moving their hands to a target location to use any of these three methods to exit OEI training mode.Finally, it is possible that the accident crew did not attempt to exit OEI training mode. Test pilot interviews suggest that, in an abnormal situation, stabilizing the aircraft would be the first priority; exiting OEI training mode may not have been considered to be an option by the accident crew.As noted earlier, the CVFDR was not operational, and possible discussions between the pilots, which may have provided information about why they did not exit OEI training mode, were not available to help determine why they did not exit OEI training mode.Postaccident Actions by the Helicopter ManufacturerSince the accident, the helicopter manufacturer has

designed a software filter for the collective control law to dampen biomechanical feedback due to oscillatory control inputs as the frequency of control input increases;

adjusted the aero-servo-elastic model with a correlation factor to incorporate the aerodynamic effects observed during flight test and the accident test to preclude such occurrences seen in the accident flight's telemetry data;

performed shake tests with pilots using a side-stick collective to determine and incorporate the transfer function for human biomechanical feedback;

modified the AHRS software filters to further reduce the AHRS response to a 6-Hz airframe vibration;

indicated that, for the accident helicopter model, cockpit audio is now being recorded by an onboard CVFDR, and communications to and from the ground monitoring station are recorded by the CVFDR and the telemetry system during all flights (cockpit video is also being recorded by the instrumentation system and archived at the ground station);

issued a company-wide business directive to ensure that cockpit audio is recorded during all telemetered flight test activities across all flight test sites;

plans to conduct flight testing in the 95% to 100% range of Nr in an OEI condition;

plans to implement, for the accident helicopter model, the unique low Nr aural tone in their test aircraft, and a software update that includes a larger font size for the Nr numeric display on the PSI;

plans to implement a separate PBA specifically for low Nr and is incorporating more salient cues into the tactile cueing system;

plans to incorporate the automatic termination of OEI training mode should Nr fall below a certain limit; and

incorporated a safety officer for the accident helicopter model test program who will have dedicated safety-related responsibilities.

Probable Cause and FindingsThe National Transportation Safety Board determines the probable cause(s) of this accident to be: A severe vibration of the helicopter that led to the crew's inability to maintain sufficient rotor rotation speed (Nr), leading to excessive main rotor blade flapping, subsequent main rotor blade contact with the tail boom, and the resultant in-flight breakup. Contributing to the severity and sustainment of the vibration, which was not predicted during development, were (1) the collective biomechanical feedback and (2) the attitude and heading reference system response, both of which occurred due to the lack of protections in the flight control laws against the sustainment and growth of adverse feedback loops when the 6-hertz airframe vibration initiated. Contributing to the crew's inability to maintain sufficient Nr in the severe vibration environment were (1) the lack of an automated safeguard in the modified one-engine-inoperative software used during flight testing to exit at a critical Nr threshold and (2) the lack of distinct and unambiguous cues for low Nr. FindingsAircraftProp/rotor parameters - Attain/maintain not possible (Cause)Main rotor blade system - Capability exceeded (Cause)Flight control system - Design (Factor)Personnel issuesUse of equip/system - Pilot (Factor)Use of equip/system - Copilot (Factor)Lack of action - Pilot (Factor)Lack of action - Copilot (Factor)Environmental issuesVibration - Effect on personnel (Cause)Vibration - Effect on operation (Cause)Vibration - Ability to respond/compensate (Cause)Vibration - Awareness of condition (Factor)Organizational issuesEquip certification/testing - Manufacturer (Factor)Interface design - Manufacturer (Factor)Equipment design - Manufacturer (Factor)Policy/procedure development - Manufacturer (Factor)Factual InformationHistory of FlightManeuveringInflight upsetAircraft structural failure (Defining event) On July 6, 2016, about 1148 central daylight time, an experimental research and development Bell 525 helicopter, N525TA, broke up in flight and impacted terrain near Italy, Texas. The two test pilots received fatal injuries, and the helicopter was destroyed. The helicopter, which was owned by Bell Helicopter Textron, Inc., was being operated under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a developmental flight test. Visual meteorological conditions prevailed at the time of the accident. The flight originated from Arlington Municipal Airport, Arlington, Texas.About 0630 on the morning of the accident, the two test pilots, flight test engineers, and a chase helicopter flight crew briefed the planned flight. The brief detailed that the accident helicopter, accompanied by a chase helicopter, would proceed to the Arlington Initial Experimental Test Area (about 30 miles south of Arlington Municipal Airport) to perform the in-flight portion of the tests. The purpose of the flight was to evaluate engine loads at maximum continuous power, two-to-one-engine simulated engine failures, longitudinal roll oscillations, and run-on landings in the heavy, forward center-of-gravity configuration.The test card for the two-to-one-engine simulated engine failure detailed that the pilots would simulate the loss of engine power from one engine while keeping both engines operating by using one-engine-inoperative (OEI) special training mode software, which reduced the power output of both engines to represent the maximum power that can be produced by one engine. When the OEI special training mode was engaged and a loss of power was simulated, the pilot would monitor rotor rotation speed (Nr) and intentionally delay his response by about 1 second before recovering from the maneuver by lowering the collective to reduce the power demanded by the rotor (and increase Nr). The lowest allowable Nr limit was identified as 86%; if Nr went below 86%, the test would be halted, and the crew would recover Nr to 103%, exit OEI special training mode, and return to steady level flight. A Bell structural engineer stated that flight below 86% Nr would result in the helicopter returning to base. During test flights, flight test engineers monitor real-time telemetry data from the helicopter under the oversight of the flight test director, who was in direct radio communications with both the test helicopter pilots and the chase helicopter pilots.About 0959, weather conditions were determined to be acceptable for the flight, and about 1038, the helicopter departed for the test area, followed by the chase helicopter. About 1048, the pilots established the helicopter's maximum level flight airspeed (Vh) at 4,000 ft density altitude (DA) as 148 knots calibrated airspeed (KCAS). After performing steady-heading sideslips, the pilots performed a series of level turns and then began the two-to-one-engine simulated engine failures.About 1108, the pilots set the OEI training mode shaft horsepower to a value predetermined by the flight engineers. The first three tests were performed in level flight at 102 KCAS, 131 KCAS, and 145 KCAS. The pilots then performed tests at 155 knots true airspeed (KTAS), 160 KTAS, 165 KTAS, and 175 KTAS, which required the helicopter to be in a shallow descent to achieve the required airspeed. These OEI tests had resulted in a rotor speed decay of 5 to 13% Nr. During these tests, to allow Nr to recover to 97% or greater, the crew lowered the collective input to near or below 50%. (100% is the full-up collective position, and 0% is the full-down collective position.) Data recorded on the helicopter's flight test recorder system, which was typically downloaded after each test flight and also transmitted via a telemetry stream to Bell's flight-test facility for real-time analysis and recording, indicate the build-up tests and recovery time required (see table 1). (Record 45 was a void record, and record 49 was aborted because of two engine torque spikes typical of wind gust encounters.)Table 1. Build-up tests and recovery time required.

During the build up to the final test, the flight test engineers received warning and alert notifications, most of which related to main rotor and tail rotor pitch link loads, pylon loads, and tail boom loads. These alerts and warnings were expected as the airspeed increased and the dynamic loads on the rotor system and airframe also increased. During most of the OEI transitions, the pilot responded by lowering the collective between 1 and 2 seconds after the simulated loss of engine power. However, with each increase in airspeed, the time the crew took to recover Nr to the target value of 103% was longer. Bell test pilots indicated that they interpreted this trend as the tendency of the crew to be more judicious while applying collective at successively higher airspeeds in order to avoid recovering too fast and overspeeding the rotor or damaging the transmission.About 1148, the final test was performed at 185 KTAS, which was the helicopter's never-to-exceed speed (Vne) at the time of the test flight; the set up and entry were the same as the previous tests. OEI was engaged, and Nr drooped to about 91% within 1.5 seconds. The Nr decay was stopped by the pilot's reduction of collective, and Nr began to recover and leveled out around 92%. The crew stopped lowering the collective at the 58% collective stick position. About 7 seconds after arresting the Nr decay (about 12 seconds into the test), the structural dynamics engineer noticed increased engine vibrations, at which point he called "knock-it-off." The test director radioed to the Bell 525 pilots to "knock-it-off," while other engineers in the telemetry room were receiving warnings and alerts and were reinforcing the "knock-it-off" call.The crew of the chase helicopter, which was positioned about 100 ft above and on the right side of the Bell 525 about 3 to 4 rotor diameters away, heard the test director call "knock-it-off" about the same time they observed the 525's rotor blades flying high and the rotor looking wobbly and slow. The chase helicopter crew radioed, "Hey, you're flapping pretty good," but the 525 pilots did not respond. About 21 seconds into the test, the main rotor severed the tail boom, and the telemetry signal was lost. The chase helicopter crew observed the helicopter's tail and fuselage jack-knife and debris separate from the helicopter. The chase helicopter crew radioed to the test director, "We've had a major accident," and landed near the wreckage to attempt assistance. Pilot InformationCertificate: Airline Transport; Flight Instructor; Commercial; MilitaryAge: 36, MaleAirplane Rating(s): Single-engine LandSeat Occupied: RightOther Aircraft Rating(s): HelicopterRestraint Used: 5-pointInstrument Rating(s): HelicopterSecond Pilot Present: YesInstructor Rating(s): Helicopter; Instrument HelicopterToxicology Performed: YesMedical Certification: Class 2 Without Waivers/LimitationsLast FAA Medical Exam: 04/11/2016Occupational Pilot: YesLast Flight Review or Equivalent: 11/06/2015Flight Time: 323 hours (Total, all aircraft), 78 hours (Total, this make and model), 245 hours (Pilot In Command, all aircraft), 37 hours (Last 90 days, all aircraft), 7 hours (Last 30 days, all aircraft) Co-Pilot InformationCertificate: Airline Transport; Flight Instructor; Commercial; Foreign; MilitaryAge: 43, MaleAirplane Rating(s): Multi-engine Land; Single-engine LandSeat Occupied: LeftOther Aircraft Rating(s): HelicopterRestraint Used: 5-pointInstrument Rating(s): HelicopterSecond Pilot Present: YesInstructor Rating(s): Instrument HelicopterToxicology Performed: YesMedical Certification: Class 2 Without Waivers/LimitationsLast FAA Medical Exam: 06/01/2016Occupational Pilot: YesLast Flight Review or Equivalent: 11/06/2015Flight Time: 756 hours (Total, all aircraft), 62 hours (Total, this make and model), 531 hours (Pilot In Command, all aircraft), 16 hours (Last 90 days, all aircraft), 2 hours (Last 30 days, all aircraft) The pilot held a letter of authorization (LOA) from the Federal Aviation Administration (FAA) dated December 2, 2015, authorizing him to act as pilot-in-command (PIC) of the Bell experimental helicopter designated model 525. He completed crew resource management (CRM) training on January 12, 2015. The pilot graduated from the United States Naval Test Pilot School (USNTPS) in 2010. He then worked on numerous flight test projects involving the Bell AH-1W (SuperCobra, a twin-engine attack helicopter) and UH-1Y (Venom/Super Huey, a twin-engine utility helicopter). On September 23, 2013, he was hired by the Bell Helicopter flight test department as a pilot for the Bell 525 program.The copilot held an LOA from the FAA dated December 2, 2015, authorizing him to act as PIC of the Bell experimental helicopter designated model 525. He completed CRM training on January 12, 2015. The copilot completed US Navy flight training in 2000 and graduated from the USNTPS in 2006. He then worked on numerous AH-1W and UH-1Y test programs. On August 2, 2010, he was hired by the Bell Helicopter flight test department as a pilot for the Bell 525 program. Aircraft and Owner/Operator InformationAircraft Manufacturer: BELLRegistration: N525TAModel/Series: 525Aircraft Category: HelicopterYear of Manufacture:Amateur Built: NoAirworthiness Certificate: ExperimentalSerial Number: 62001Landing Gear Type: Retractable - TicycleSeats: 2Date/Type of Last Inspection:Certified Max Gross Wt.: 21419 lbsTime Since Last Inspection:Engines: Turbo ShaftAirframe Total Time:Engine Manufacturer: General ElectricELT: Installed, not activatedEngine Model/Series: CT7-2F2Registered Owner: Bell Helicopter - TextronRated Power:Operator: Bell Helicopter - TextronOperating Certificate(s) Held: Certificate of Authorization or Waiver (COA)The accident helicopter was a conventional main rotor and tail rotor design (see figure 1). On April 25, 2016, the helicopter received its latest experimental research and development airworthiness certificate from the FAA. The helicopter was a manufacturing prototype being developed for certification as a transport-category helicopter in compliance with 14 CFR Part 29. As part of the airworthiness certificate, the FAA issued an operating limitations document (also dated April 25, 2016) that specified the following: pilots operating the helicopter must hold a temporary LOA issued by an FAA flight standards operations inspector to act as PIC, the helicopter must be maintained by an FAA-approved inspection program, day visual flight rules flight operations are authorized, and all flights must be conducted within the Arlington Initial Experimental Test Area. The helicopter was estimated to weigh about 19,975 lbs at the time of the accident.

Figure 1. Accident helicopter (Bell 525, N525TA).Source: Bell HelicopterThe Bell 525 helicopter had a five-bladed main rotor that provided helicopter lift and thrust and rotated in a counterclockwise direction when viewed from above. The main rotor was a fully articulated system that used elastomeric bearings to accommodate blade feathering, flapping, and lead-lag motions. Fluid-elastic dampers moderated lead-lag motion of the blades. The five main rotor blades were identified by colored stickers, presented in order of advancing rotation (when seated in the pilot seat and observing the blades pass from right to left): blue, orange, red, green, and white. The Bell 525 also had a four-bladed, fully articulated, canted tail rotor that provided thrust to counteract main rotor torque effect, control helicopter yaw, and provide lift. The four tail rotor blades were identified by colored stickers, presented in order of advancing rotation: blue, orange, red, and green. The helicopter was equipped with two General Electric (GE) CT7-2F1 turboshaft engines, mounted aft of the main transmission, and one Honeywell RE100BR auxiliary power unit (APU), mounted between the two engines at the aft end of the engine deck. The helicopter was equipped with a triple-redundant fly-by-wire flight control system with a triplex hydraulic system. Additionally, the helicopter was equipped with retractable tricycle landing gear.The cockpit was configured for two pilots in a side-by-side seated position and a center console between them. Each pilot had a cyclic side-stick controller forward of the seat's right armrest, a collective side-stick controller immediately forward of the seat's left arm rest, and a set of pedals forward of their feet. The instrument panel consisted of four identical primary flight display (PFD)/multifunction display (MFD) panels. The center console had two Garmin Touch Control (GTC) panels, the landing gear handle, the Nav/Com panel, and the flight test switch panel, which included some controls for the OEI special training mode software. Directly above the GTCs were the engine control COSIF (crank, off, start, idle, fly) knobs. Each pilot had an additional pilot display unit that provided real-time flight test instrumentation parameters such as DA, boom airspeed, mast airspeed, engine torque, load factor, pitch/yaw/roll rates, slip angle, and main rotor and tail rotor flapping angles.OEI Training ModeOEI training mode is a specific GE software-driven capability that permits simulation of a single-engine failure without actually rolling back or shutting down an engine in flight. When the flight crew engages the OEI training mode, both engines reduce power to represent the power available from a single engine. Consistent with normal operations and depending on the flight conditions, if the power demanded by the rotor exceeds the power available, Nr will droop. If single-engine power is insufficient to sustain the forward speed, the pilot must reduce the power demand by lowering the collective control, applying aft cyclic (to reduce speed), or using a combination of both. Nr increases to 103% when the power required matches the single-engine power available.To engage OEI training, the pilot or copilot navigates to the OEI training page on the GTC and selects the engine to fail on the touch screen. Once selected, a green bar appears on the failed engine button to signal that OEI training mode was engaged (see figure 2). When OEI training mode is engaged, the pilot's side (right-seat) PFD displays simulated OEI engine values, and the copilot's side (left-seat) PFD displays the actual all-engines-operative (AEO) data.

Figure 2. OEI training page on the GTC.Source: Bell HelicopterThe OEI special training mode that Bell used for the accident flight test did not incorporate an automatic disengagement of OEI training mode for low Nr. Bell modified the production version of OEI training mode software, originally created by GE, to eliminate a safeguard that automatically exited the OEI training mode when Nr fell below 90%. According to Bell, automatic disengagement at 90% Nr was not low enough to allow development and demonstration of OEI recovery across the flight envelope during testing, and a lower Nr value for automatic disengagement was deemed unnecessary due to the highly controlled test environment. To manually exit OEI training mode, the pilot could (1) press the engine fail button on the GTC (the same button used to engage OEI training mode), (2) exit the OEI training page on the GTC (using the BACK button), or (3) move the COSIF switch to a position other than "Fly" and then return the switch to "Fly." The Bell 525 lead test pilot indicated in a postaccident interview that the options to exit OEI training mode were not discussed formally with all the test pilots but were specifically discussed with the accident test pilot. Bell 525 test pilots interviewed said that they almost always press the engine fail button on the GTC to exit OEI training mode; some Bell pilots were aware of the other methods to exit OEI training mode while other test pilots were not. Disengaging OEI training mode would make both engines available to provide full power to restore the reference Nr to 100% if the rotor was in a drooped state.The production OEI training mode, which will be used in Bell 525 production helicopters, includes an automatic disengagement of OEI training if Nr decays below 90% (pending validation via testing). In the production OEI training mode, automatic exit would occur in the following circumstances:-Loss of an engine.-Torques of the two engines are not within ~30 ft-lb of each other.-There are any significant engine failures (any fault that would cause local channel degraded on any of the 4 channels). If the enable bit for training is set (bit 20) AND both engine request bits are set (bit 21 and 22). To engage training only one-engine request bit can be set.-Power turbine speed (Np) is 5% below the reference value (having previously been within 1% of the reference while in training) or to a value below 90%.-Np is above 106%.-Real engine gas producer turbine speed is above 106%.-Real engine measured gas temperature is above 1934.3° F/ 1056.8° C.-Real single-engine torque is above 521 ft-lb (67.7%).-Real engine oil temperature is above 148.89° C.-Low oil pressure switch is tripped.OEI training mode flight test risk analysis worksheets documented planned operational risk mitigation for OEI training. A worksheet approved on June 29, 2015, included a discussion of the risk of low Nr, and a worksheet approved on April 1, 2016, included a discussion about engine overtorquing.Power Situation Indicator (PSI)The PSI was located in the bottom left corner of the PFD for each pilot. The bars in the bottom right corner of the PSI represented Np for the number 1 engine, Nr, and Np for the number 2 engine, respectively. The arc in the center of the display depicted the percentage of engine value compared to its limit (see figure 3).

Figure 3. Example of PSI on the Bell 525.Source: Bell HelicopterIndications of Low Rotor Rpm in the Bell 525Power Situation IndicatorThe PSI displayed Nr as a vertical scale (center bar in lower right indicator) when Nr was above 90%, as shown in figure 3. If Nr dropped below 90%, the display changed to an analog needle that displayed a green arc for Nr between 100 and 90%, a yellow arc for Nr between 86 and 89% Nr, and a red arc below 86% Nr (see figure 4). (Overtorquing limits appear above 100%.)

Figure 4. PSI displaying Nr as an arc.Source: Bell HelicopterThe CAS was located in the middle right side of the PFD and displayed color-coded messages for status, advisory, caution, and warning alerts (see figure 5). The Bell 525 lead test pilot described warnings as items that need immediate attention and cautions as items that will need attention but not immediately. (Warnings were displayed as white text on red background, cautions were displayed as yellow text on black background, advisories were displayed as white text on black background, and status messages were displayed as green text on black background.) When warnings and caution alerts were triggered, the displayed messages would flash until either the cockpit master warning/caution push button annunciator (PBA) was pressed, the bezel button on the lower right corner of the PFD was pressed, or the triggered condition was inactive for more than 5 seconds. In addition, a caution/warning flag would appear in the lower right corner of the PFD, and a caution/warning light would illuminate on the PBA. For the accident helicopter, if Nr dropped below 90% (in AEO or OEI), a "ROTOR RPM LO" warning-level message appeared (see figure 6). Once the condition cleared, the message would immediately disappear.

Figure 5. Location of visual CAS information available to crew.Source: Bell Helicopter (modified by the National Transportation Safety Board)

Figure 6. Example of PFD during "ROTOR RPM LO" warning.Source: Bell HelicopterAn aural tone also annunciated with a CAS alert. The technical requirements specification indicated that the caution audio tone would be a "ping" decaying over 0.5 second that sounded when each caution or warning message activated, the warning audio tone would be three "pings," and the low rotor rpm tone would be a unique continuous low/high/low warble to be played continuously as long as the condition existed or until muted.In the accident helicopter, the aural tone annunciated for "ROTOR RPM LO" was a master warning tone that was not unique to low Nr and was associated with at least 21 other warning messages. The Bell 525 lead test pilot indicated that, during the experimental flight test, many of the aural messages were still under development; the tones had been selected but not implemented. The test team determined that having some aural indication for low Nr was sufficient for development flight testing. He stated that the accident crew had flown OEI tests previously and had conducted autorotation testing with test conditions that would likely have triggered the low Nr warning. He also stated that the crew was likely exposed to the master warning for low Nr during flight testing and in the Relentless Advanced Systems Integration Laboratory (RASIL). (More information about the RASIL can be found in the Organizational and Management Information section.)The chief pilot of the Bell test program stated that, without information from the PFD, he would rely on rotor aural cues to gauge rotor speed. The Bell 525 lead test pilot stated that, lacking any instrument indication, pilots could usually determine rotor speed (high or low) by the sound: specifically, they could hear an engine winding down or sense higher vibrations at higher airspeeds. The Bell 525 lead test pilot further indicated that, under normal conditions, pilots can hear the decrease in Nr and would be able to tell the difference between 100% and 92% Nr but given the vibration environment during the accident flight, it is uncertain whether the pilots would have heard the low Nr.Summary of Low Nr Indications for the Accident Flight CrewTable 2. Indications to the accident flight crew regarding low Nr during the event profile.

MaintenanceDuring the experimental ground and flight testing of the accident helicopter, discrepancies and anomalies were recorded, prioritized, and tracked. Aircraft systems interim procedures (ASIP) provided instructions for periodic or on-condition inspection and/or maintenance. Inspection tasks, including those required by ASIPs and experimental engineering orders, were logged into a database with comments, including inspection results. Recent maintenance performed on the accident helicopter before the accident flight included the following:-A nondestructive inspection and tap test of all four tail rotor blades (no damage noted).-A detailed visual inspection of the tail rotor hub (no damage noted). -A torque check of the pylon beam attaching hardware (no movement of the attaching hardware noted).-A recurrent inspection of airframe longerons required by an ASIP (no anomalous findings reported). Meteorological Information and Flight PlanConditions at Accident Site: Visual ConditionsCondition of Light: DayObservation Facility, Elevation:Observation Time:Distance from Accident Site:Direction from Accident Site:Lowest Cloud Condition:Temperature/Dew Point:Lowest Ceiling:Visibility:Wind Speed/Gusts, Direction:Visibility (RVR):Altimeter Setting:Visibility (RVV):Precipitation and Obscuration:Departure Point: Arlington, TX (GKY)Type of Flight Plan Filed: Company VFRDestination: Arlington, TX (GKY)Type of Clearance: UnknownDeparture Time: 1035 CDTType of Airspace: Arlington Municipal Airport is located 31 miles north-northwest of the accident site. The Arlington automated surface observation system (elevation 628 ft mean sea level [msl]) recorded observation for 1145 was wind from 170° at 15 knots, 10 miles visibility, sky clear of clouds, temperature 32°C, dew point 23°C, and altimeter of 29.95 in Mercury (Hg).Hillsboro Municipal Airport is located 15 miles south-southwest of the accident site. The Hillsboro automated weather observation system (elevation 686 ft msl) recorded observation for 1136 was wind from 190° at 16 knots with gusts to 22 knots, 10 miles visibility, scattered clouds at 3,000 ft, temperature 31°C, dew point 23°C, and altimeter at 29.98 in Hg. Wreckage and Impact InformationCrew Injuries: 2 FatalAircraft Damage: DestroyedPassenger Injuries: N/AAircraft Fire: On-GroundGround Injuries: N/AAircraft Explosion: NoneTotal Injuries: 2 FatalLatitude, Longitude: 32.246111, -96.919722 (est)The main wreckage field was 2,200 ft from the last transmitted GPS point, along the flightpath heading of 320°. The main wreckage site included an impact crater, remnants of the main fuselage, cockpit, main transmission and main rotor hub, two of the five main rotor blades (blue and green), the forward portion of the tail boom, and both engines. There was evidence of a postcrash fire at the main wreckage site. The wreckage debris path at the main wreckage site was about 200 ft in length and was oriented about 315° magnetic.The secondary wreckage site was about 1,300 ft southeast of the main wreckage site and comprised the aft portion of the tail boom, which contained the tail rotor drive system, intermediate gearbox, tail rotor gearbox (TRGB), and tail rotor. A debris field extended between the last data point and the main wreckage covering about 4,000 ft (north to south) by 1,700 ft (east to west). Three of the five main rotor blades (orange, white, and red) and various pieces of forward cowlings, cockpit frames, and cabin doors were found separate from the main and secondary wreckage sites in the debris field. Additionally, lightweight debris, such as insulation and main rotor blade skin pieces, was found scattered to the northeast of the debris path between the main and secondary wreckage sites, with the farthest piece being found about 1,520 ft away from the debris path between the main and secondary wreckage sites (see figure 7).

Figure 7. The location of the main wreckage site, secondary wreckage site, and selected items from the wreckage debris field.The main fuselage was highly fragmented and exhibited evidence of thermal damage. The cockpit wreckage did not sustain significant thermal damage. Fractured pieces of the cyclic and collective side sticks were observed within the cockpit wreckage. The lateral push-pull tubes were retained in the cockpit wreckage but exhibited fractures consistent with overload. Both engines remained installed on the engine deck and exhibited thermal distress from exposure to the postcrash fire. The forward portion of the tail boom exhibited an angled fracture line at its aft end consistent with main rotor blade contact. The tail boom attachment points to the main fuselage exhibited fractures near the upper left corner and lower right corner. The aft portion of the tail boom was found resting partially inverted, with the tail rotor head and one tail rotor blade wholly embedded into the ground and exhibited an angled cut line at its forward end consistent with main rotor blade contact (see figure 8).

Figure 8. Angled cut line at the forward end of the aft section of the tail boom.Source: GE AviationThe main rotor hub remained attached to the main rotor shaft. The inboard end of the blue main rotor blade exhibited evidence of thermal damage, and the root end of the blade airfoil remained attached to its respective grip assembly via three blade retention bolts. A 14-ft-long inboard section of the orange main rotor blade was found about 1,140 ft southeast of the main wreckage site with its inboard end embedded in the ground and its outboard end embedded in tree branches; the remainder of the blade was found about 2,880 ft southeast of the main wreckage site. Yellowish-orange paint transfer marks (similar in color to the primer found on portions of the airframe) were observed on the leading-edge surfaces in the area where the blade fractured into two distinct pieces, and additional orange paint transfer marks were observed on the leading-edge surfaces. Gouge marks into the lower blade surface and damage to the blade afterbody were observed. The red main rotor blade was found embedded in a tree about 1,400 ft southeast of the main wreckage site; impact marks on the leading edge, a fracture on the spar, and a chordwise gouge on the lower surface of the blade were observed. An inboard section of the green main rotor blade was recovered adjacent to the main transmission at the main wreckage site, and a 9-ft-long outboard section of the blade was found in a tree canopy about 1,325 ft southeast of the main wreckage site. The white main rotor blade was found on the ground about 350 ft southeast of the main wreckage site; the upper and lower grips were both fractured, while the blade airfoil remained attached. The blade leading-edge abrasion strip exhibited impact marks that included orange and yellow paint transfer marks.The tail rotor head remained attached to the TRGB and exhibited no evidence of cracks or fractures. The blue tail rotor blade leading edge was partially embedded into the ground; a small puncture was observed on the outboard surface. The orange tail rotor blade leading-edge tip was found embedded into the bottom-left edge of the tail cone; the orange tail rotor blade tip end afterbody exhibited a mid-chord fracture extending about 10 inches inboard. The red tail rotor blade trailing edge was partially embedded into the ground. The green tail rotor blade was wholly embedded into the ground; removal of the tail rotor revealed the blade airfoil had partially folded over immediately outboard of the grip attachment. Three of the four tail rotor dampers remained intact and were able to be bench tested; the fourth tail rotor damper separated into two halves and could not be bench tested. Dynamic bench testing of the three tail rotor dampers did not reveal evidence of anomalous response behavior.Flight RecordersThe accident helicopter was equipped to carry a pilot and copilot with no passengers and was not required to be equipped with either a flight data recorder (FDR) or cockpit voice recorder (CVR) under the provisions of 14 CFR 91.609. A combination CVR and FDR (CVFDR) was installed but was not operational at the time of the accident. (When certified as a transport-category rotorcraft under 14 CFR Part 29, the Bell 525 will be equipped with both CVR and FDR recording capabilities.) The accident helicopter was heavily instrumented with several aircraft- and ground-based recording systems, both production and flight-test based, including a streaming telemetry system, helicopter monitoring unit (HMU), avionics recorders, and PFD/MFD recording capability.The National Transportation Safety Board (NTSB) received the following components with flight data recording and storage capabilities: Simmonds Precision Products Vigor HMU (serial number [S/N] 0006); CVFDR (S/N 009-01029); 128 gigabyte (GB) solid-state drive (SSD) from aircraft high-speed avionics bus (S/N TW-032GYJ-55085); 4 SD memory cards (S/N unknown); and Zodiac Aerospace remote storage module (RSM) 128 GB (S/N 052405-112012). Regarding the HMU and 4 SD memory cards, all the data was available from other sources. Regarding the CVFDR, the data download file was determined to be blank; the FDR may not have been receiving data or been fully configured in the helicopter. Regarding the SSD, due to the extent of the damage, no data could be recovered.Zodiac Aerospace RSM 128 GBThe Zodiac Aerospace RSM, the data storage medium of the flight test recorder system installed on N525TA, is a solid-state hard drive with 128 GB capacity and an integrated E-SATA download interface. The data recorded on this drive, which was typically downloaded after each test flight, was the primary data source for Bell's flight test analysis team and was sourced from the following sensors and aircraft systems:

Production accelerometers in the drive system, rotors, and engine/APU.

Flight controls data bus including ARINC-429/1553/RS-232/RS-485.

Hydraulic system temperatures, pressures, and flows.

Production and flight test air data systems, including temperatures and pressures.

Both engines, all engine control channels of temperatures, pressures, speeds, gearboxes, and shafts.

Flight test temperature readings in the aircraft skin.

Avionics and flight displays systems.

The data stream recorded by the RSM was also transmitted via a telemetry stream to a ground station at Bell's flight-test facility for real-time analysis and recording.The RSM, which was ejected from the helicopter during the crash sequence and was found apart from the main wreckage, was in good condition, with no apparent impact or thermal damage. Bell extracted the data under the NTSB's supervision. The RSM recording contained about 1 hour 26 minutes of data, including preflight and flight activities; the event flight was the only flight recorded on the drive. Once processed, the data was segregated into "prime" data (data taken during a test) and "non-prime" data (data taken at all other times). There were 41 periods of prime data in the recording, including the period up to and including the end of the recording. The RSM engine data showed that the engines were operating as commanded throughout the flight. (More information about test 51 can be found in the Tests and Research section.)Medical And Pathological InformationThe Office of the Medical Examiner for the county of Dallas, Texas, performed an autopsy on the pilot and determined that the cause of death was thermal and blunt force injuries.The FAA Bioaeronautical Sciences Research Laboratory performed toxicology testing on specimens from the pilot. The specimens were noted as being putrefied; tests for carbon monoxide and cyanide were not performed, ethanol was detected in muscle, no ethanol was detected in the brain, and none of the listed drugs in the toxicology report were detected in the liver specimen.The Office of the Medical Examiner for the county of Dallas, Texas, performed an autopsy on the copilot and determined that the cause of death was blunt force injuries.The FAA Bioaeronautical Sciences Research Laboratory performed toxicology testing on specimens from the copilot. The specimens were noted as being putrefied; tests for carbon monoxide and cyanide were not performed, ethanol was detected in muscle, no ethanol was detected in the liver, propanol was detected in muscle, and none of the listed drugs in the toxicology report were detected in lung or liver specimens.Tests And ResearchThe helicopter's flight telemetry system recorded flight data on the aircraft and streamed it to the test crew monitoring the flight from the ground. The lowest data collection rate was 31.25 hertz (Hz) and the highest was 4,000 Hz. Data was recorded continuously throughout the test and then divided into identifying records for each test point performed. When the pilot initiated a new test, the test timer started from zero. The helicopter was on test 51 (which ran for 21.18 seconds) when the accident occurred, indicating it was the 51st flight test point on the day of the accident.For the Vne of 185 knots, a single engine is insufficient to maintain the flight condition; management of Nr is critical to recovering from the loss of an engine. Pilot response at high speed is to lower the collective to reduce torque on the rotor and/or to pull the longitudinal cyclic back to reduce the airspeed; both actions result in reducing the power required by the main rotor and allowing Nr to recover. Once rotor speed has recovered to the target value of 103% Nr, the test would be considered complete.In two prior successful OEI tests at 175 knots airspeed (record 50) and 165 knots airspeed (record 48), Nr decayed from 100% within about 3.5 to 4 seconds, consistent with initiation of the OEI test. Collective was reduced to 51% for test 50 and 43% for test 48. Nr stopped decreasing around 90% before recovering to 97% for test 50 and nearly 100% for test 48. The time from Nr decay to initial Nr recovery for both tests was between 2 and 3 seconds (see figure 9).

Figure 9. Plot comparing tests 48, 50, and 51.For test 51, Nr began to decay about 3.5 seconds after test initiation, similar to the prior tests. Collective was reduced to 58%, and Nr stabilized near 92% but did not return to 97% or higher as in the previous tests. After 6 seconds, a vibration near 6 Hz was seen in the collective and longitudinal cyclic inputs that was not present in the earlier tests. After 7 seconds, Nr stopped recovering. When collective was increased between 10 and 13 seconds and again between 16 and 17.5 seconds, Nr slowed, and, by 18 seconds, it had decreased to below 80%. After 10 seconds, cyclic input activity increased, as did the roll response. The helicopter's roll and pitch responded to cyclic input throughout the accident flight.The red main rotor blade was instrumented to record blade flapping; as Nr decreased after 16 seconds, the out-of-plane flapping motion increased. At 20.4 seconds, the string potentiometer that measured blade flapping motion stopped functioning due to excessive flapping. At 20.7 seconds, a large aft cyclic input reached peak value. Within two rotations of losing the flapping signal, one or more of the main rotor blades severed the tail boom from the aircraft, and all data recording and telemetry ended.As noted above, an oscillation occurred in the collective and cyclic control inputs during the accident test sometime after 6 seconds; the oscillation was not present during the previous test records and indicated a vibration in the structure and controls near 6 Hz. This vibration was not a single mode of vibration at exactly 6 Hz throughout the flight; the frequency of the vibration changed slightly through the test as rotor speed changed and various airframe and rotor modes were excited. This 6-Hz vibration was distinctive, grew in amplitude, and affected the entire helicopter and the flight crew.After 7 seconds, the vibration was well defined, and the amplitude began to grow. At 10 seconds, the amplitude grew before decaying again after 12 seconds. (This growth was described as a "blossom" in the vibration.) The appearance of the 6-Hz oscillation corresponded with an Nr of about 92%. As Nr stayed near 92%, the 6-Hz vibration grew in amplitude from around 7 seconds until 11 seconds. At 11 seconds, Nr slowed below 90%, and the 6-Hz amplitude decreased. At 13.5 seconds, Nr began to increase from 86%, and as Nr again approached 92%, the 6-Hz amplitude increased. The amplitude of the vertical acceleration was near ± 2.5 G at 6 Hz around 11 seconds and again after 16 seconds. (G is a unit of measurement of acceleration; 1 G is equivalent to the acceleration caused by the earth's gravity [about 32.2 ft/sec2].) For comparison, earlier test records showed variations in vertical acceleration no greater than ± 0.3 G. The 6-Hz vibration appeared in the control inputs, especially the collective, starting before 7 seconds.The investigation focused on the source of the 6-Hz vibration. The lead-lag (in-plane) motion of a rotating rotor system can produce frequencies in the fixed (nonrotating) system (the frequency at which the rotor system conveys motion into the fixed system). The investigation focused on two significant in-plane rotor modes: the cyclic regressing mode and the scissors mode. (A cyclic mode occurs when rotor blades lead and lag in such a way that the hub of the rotor begins to orbit about its axis of rotation. The mode is regressing if the time it takes the hub to make one full cycle is slower than one full rotation of the blades around the hub. For the scissors mode, the lead-lag motions of the blades act in such a way that adjacent blades move together and apart in a scissoring motion. In forward flight, the scissors mode produces a fore-aft motion of the main rotor mast due to aerodynamic forces.) The fixed-system frequency of the main rotor cyclic regressing mode is 2.6 Hz at 100% Nr and drops to 2.4 Hz at 92% Nr. The fixed-system frequency of the main rotor scissors mode is 6.8 Hz at 100% Nr and drops to 6.2 Hz at 92% Nr. The fixed-system frequency of the tail rotor cyclic regressing mode is 6.6 Hz at 100% Nr and 5.4 Hz at 92% Nr.During the accident test, the main rotor scissors mode was excited, unexpectedly, at a lower frequency in the fixed system due to the lower Nr. Initially, as Nr was between 100% and 93%, the tail rotor primarily exhibited cyclic regressing in-plane motion, and the pilot-seat vertical vibration frequency followed that frequency. The amplitude of this response was less than 0.2 Gs and consistent with prior tests. At the start of the accident test, the main rotor primarily exhibited cyclic regressing in-plane motion, which was expected. At 92%, the tail rotor in-plane cyclic regressing mode and the first vertical bending mode of the helicopter coalesced near 5.4 Hz. (The first vertical bending mode is the lowest frequency mode at which the aircraft fuselage oscillates about its lateral axis [both nose and tail flex up, then both nose and tail flex down relative to the center portion of the fuselage].) As Nr decreased toward 92%, the primary main rotor in-plane motion shifted from cyclic regressing to scissors. Around 92%, the main rotor scissors in-plane motion was near 6 Hz, and, by 6.5 seconds, the pilot-seat vertical acceleration responded at the main rotor scissors mode frequency, indicating that the fuselage of the aircraft was responding to the scissors mode. The main rotor's shift to the scissors mode produced a frequency around 6 Hz that began dominating the vibratory signature of the tail rotor and the fuselage and, by 7 seconds, had affected the controls.From 5 to 11 seconds, Nr stayed between 90% and 93%, and the amplitude of the pilot-seat vertical acceleration increased markedly from less than ± 0.1 G to greater than ± 1 G. After 12 seconds, a collective control increase resulted in a further reduction in Nr, which coincided with a reduction in the pilot-seat vibration about the 14-second mark. As the test continued, the amplitude of the vibration grew again in all channels where it was present.Two sources were determined to have increased the amplitude of the helicopter's 6-Hz frequency response:

Biomechanical feedback into the collective control

Cyclic stir in the swashplate driven by the attitude and heading reference system (AHRS)

Determining the separate contributions of the biomechanical feedback and the AHRS to the increase in amplitude was not possible with the flight data. The evidence for biomechanical feedback is seen in the trace of pilot collective control after 6.5 seconds, which shows the pilot's control stick moving at the 6-Hz frequency. The pilot's collective control oscillations result in further amplification of the main rotor scissors mode, further amplifying the vertical seat vibration and increasing the collective stick oscillation. Since the collective was being physically cycled at 6 Hz, the control laws would send a corresponding (6-Hz) command to the tail rotor as antitorque compensation. The biomechanical feedback loop appears to attenuate after 10 seconds (and again at 16 seconds as seen by reductions in the pilot-seat vertical vibration and collective control oscillation at those times).During the accident flight, excitation of the airframe's first bending modes (lateral and vertical) induced the AHRS to respond with inputs intended to stabilize the aircraft. The AHRS was intended to work with the control laws as though the fuselage was a rigid body responding to wind gusts or similar low-frequency inputs and was not intended for handling a 6-Hz vibration. Although the AHRS included filters on the signal outputs, the filters did not specifically target the 6-Hz stirring commands to the swashplate. The stirring actions of the AHRS system at this (~6 Hz) frequency were considered to be a driver of the scissors mode amplification of the main rotor.The main rotor scissors mode had been encountered at 100% Nr (and produced a 6.7-Hz vibration) in two previous tests at lower airspeed but in high load-factor banked turns, where the rotor blades are highly loaded. Specifically, in the previous tests, when Nr was 100%, the scissors mode was at 6.8 Hz as expected. The tests were at a lower airspeed (145 to 152 knots) but included high blade loading due to increased load factor in a banked turn. In both tests, the vibration quickly damped out as the blade loading was reduced. Previous experience demonstrated that the scissors mode was well damped at 100% Nr. The high forward speed of the accident test produced a similar highly loaded aerodynamic environment for the rotor blades. One aspect of the main rotor's aerodynamic environment can be described by examining the aircraft's advance ratio (true airspeed/blade tip speed) in relation to the blade loading. High blade loading and high advance ratios produce a more complex aerodynamic environment. In all tests, the scissors mode response was only encountered on the outer edge of the blade-loading/advance ratio environment and indicate that a complex aerodynamic environment was needed to excite this response.While the scissors mode was quickly damped out in the earlier tests, it grew in amplitude during the accident test record until the whole aircraft was vibrating at that frequency. The lower frequency of the scissors mode during the accident test due to the reduced Nr allowed biomechanical feedback into the controls, and the response of the AHRS system through the control laws increased the amplitude of the scissors mode response. The manufacturer will focus on mitigating the biomechanical feedback and the AHRS-induced swashplate stirring via control law filtering to prevent the amplification of the scissors mode response.The vibration loads experienced during the accident test were outside the parameters for certification testing for the Garmin PFD and GTC displays. Because of the criticality of the PFD and GTC for flight information, a postaccident test was conducted to observe the performance of these displays when exposed to unusually high vibration loads. The displays were mounted onto a shake table, and a vibration profile similar to the accident was applied to the hardware. The GTC and PFD functioned normally throughout the entire test, and no faults were recorded. Displays presented information continuously with no distortion or screen blanking, and touch functionality on the GTC and bezel button functionality on the PFD functioned properly. Organizational And Management InformationThe Bell 525 program consisted of the conceptual design phase, preliminary design review, critical design review, flight readiness review (FRR), developmental flight testing, and certification flight testing. Investigators interviewed Bell design and test engineers who described the pace of the Bell 525 program at the time of the accident as fast but not unreasonably so. Personnel described specific pressure felt during the time of the first flight test in Amarillo, Texas, in mid-2015. When personnel were supporting the first flight, they commonly worked 7 days per week and logged between 60 and 70 hours of work per week. Many described morale to be low during the first flight. Once the flight test program moved back to Arlington, Texas, in September 2015, the pace slowed, and many reported improved morale. Original certification for the Bell 525 was scheduled for mid-2016, but the program faced various setbacks during initial design. Most engineers interviewed stated that they had not received undue pressure from management to complete tasks. No monetary incentives (outside of overtime pay) were provided to employees, and employees were not concerned about negative consequences when raising concerns. Employees described Bell's safety culture as "good." At the time of the accident, design and test engineers reported working about 10 hours of overtime per week on average.The chief engineer for the Bell 525 program was responsible for all 525 testing, certification activity, and structures (drive, rotor, and airframe). Six discipline areas reported to the chief engineer: airframe engineering, systems engineering and certification, rotors engineering and component test, drive systems, flight technology, and flight test/experimental test and evaluation. The 525 program flight test integrated product team (IPT) consisted of 12 flight test engineers and 3 instrumentation engineers. Six of the 12 flight test pilots in Bell's experimental test and evaluation department were assigned to support the 525 program. The chief engineer worked closely with the air vehicle IPT; the air vehicle lead was responsible for flight control system and software, control laws, avionics, electrical system, propulsion, hydraulic system, fuel system, and environmental controls.According to a Bell avionics engineer, before the FRR, the avionics group developed a spreadsheet of all the CAS functions and whether they were designated as critical or not critical for flight safety; they tested the safety-of-flight functions using scripts or a CAS manual test. The results for each function were "passed," "passed with exception," "failed," or "safe." A "failed" state indicated that the alert did not annunciate or annunciate in time.According to the Bell 525 lead test pilot, if no pilot action was required, then the alert would be an advisory or would only be available on the maintenance page. If pilot action was required, they referred to the following CAS philosophy: for anything requiring pilot action immediately, it was a warning; if it required action, but not immediately, it would be a caution; or, if action was required much later, it would be advisory information. The Bell 525 lead test pilot described the difference between caution and advisory as a gray area. "Safety critical" referred to messages for which if nothing was done, it would "break the helicopter, or cause the helicopter not to be flown right, or it would exceed a limit." All the warnings counted as safety critical, as did some cautions. He stated that the decision for what was critical came from the cockpit working group, which worked with other systems groups, pilots, a safety representative, and the individual who conducted design safety analysis, and all the decisions were documented. The cockpit working group created the list of safety-critical items. The list was then vetted and sent to the avionics group for implementation.According to Bell Helicopter, test pilot duties included planning and conducting experimental flight tests in helicopters and tiltrotor aircraft; conducting other flight test operations; maintaining flight currency and traveling in support of Bell Helicopter flight operations; completing flight analysis and flight evaluations of aircraft, test planning, and flight test reports; planning and executing engineering and experimental test flights of new aircraft and/or systems; evaluating and reporting on data gathered during test flights; demonstrating safe and efficient test planning and execution; interfacing with the project team to ensure successful accomplishment of the test program; and making recommendations regarding operational effectiveness of systems, aircraft handling qualities, and design improvements.In December 2015, the flight test group had put in place a personal risk assessment tool that each pilot could complete before flying. Pilots were encouraged to fill out the risk assessment every day; it was not mandatory. The accident pilots did not have a risk assessment on file for the day of the accident.The majority of pilot training consisted of time in the RASIL engineering simulator, which is an accurate engineering representation of the cockpit, including control feel, and visual in-flight representation projected on a screen that wrapped around the cockpit. Next to the RASIL cockpit was a separate "Rig Room" containing actual flight hardware (hydraulic servos) rigged to apply flight loads into engineering representations of related hardware. When a control was moved in the RASIL cockpit, hardware would respond to the command in the Rig Room. Pilots assigned to the 525 program would routinely operate the RASIL while developing flight procedures, validating software changes, and reviewing fight test plans.Although there were no written logs showing when a pilot or flight crew worked in the RASIL, the Bell chief test pilot believed the accident flight crew had reviewed the test card for the mishap flight in the RASIL, and the RASIL engineers stated that the accident flight crew routinely worked in the RASIL. Typical training flow would involve two RASIL sessions for each test flight. If the pilots had been in the RASIL within 2 weeks of a test flight, they were considered current.Additionally, both the pilot and copilot had accumulated many ground testing hours validating the OEI training mode in the helicopter.Two pilots from the flight test group were scheduled as the chase aircrew flying a Bell 429 helicopter. The duties of the chase helicopter included monitoring the test area for other aircraft, monitoring the flight for safety issues, and observing and monitoring the test helicopter as it executed the test card.The chase helicopter was in radio communications with the test helicopter and the test director. After a few circuits of the traffic pattern, the chase helicopter positioned itself behind the test helicopter, and they departed to the test area as a flight of two. Once in the test area, at the higher test airspeeds, the chase helicopter would fall farther behind the test helicopter because of its airspeed limitations but would rejoin the test helicopter as it slowed and recovered from the maneuver. The chase helicopter crew reported seeing no distractions or abnormalities outside of the accident helicopter. Additional InformationDevelopment of Biomechanical Filters on CollectiveBiomechanical feedback in the aircraft design industry refers to unintentional control inputs resulting from involuntary pilot limb motions caused by vehicle accelerations. Biomechanical feedback is usually addressed using control friction and control input filtering. The accident helicopter did not have a filter on the collective control to address biomechanical feedback. Bell engineers stated that past experience had never shown a need for filtering the collective control. Filters did exist in the cyclic control to address pitch and roll rates in addition to biomechanical feedback.Bell used a control diagram used for aero-servo-elastic analysis on the Bell 525. Before the accident, the model did not use correlation factors (modeling adjustments based on flight test data), model the main rotor in-plane scissors mode oscillations, or incorporate collective pilot biomechanical feedback in the vertical axis. The pilot model provided gain values in each axis in terms of "inches of stick per g of acceleration." In the cyclic control, the pilot model was developed using experimental data where pilots were shaken laterally on a shake table. This shake-table analysis was done for a side-stick cyclic configuration and a traditional-stick cyclic configuration. Shake-table analysis was never performed on the collective control (traditional stick or side stick) using vertical acceleration. Engineers said that they had never seen negative stability during flight test or in flight when using a pass-through filter for the collective. The control laws engineer for the Bell 525 described that their goal was to manage lag at the 1- to 2-Hz frequency for pilot control. A filter at the higher frequencies could still introduce lag at the lower frequencies. Filters would not be added unless deemed necessary for the high-frequency stability while tuned in order to not decrease margins at low frequencies.When Bell developed feedback filters, control law engineers designed for "no adverse effects" on handling qualities. They usually only discussed critical items. The control engineer interviewed did not recall that the vertical axis was deemed critical from a biomechanical feedback standpoint. For the vertical axis, filters were only added if needed, based on flight testing. The control laws engineer said that had they built a pilot model for the collective side stick with a shaker mock up, they could have developed a more accurate transfer function, but they may not have known to add an aerodynamic factor to it for main rotor regressive scissors mode. Even with an aerodynamic model, they would not have been able to validate it without the accident data. He suggested that, for flight testing, they could have tested the lower Nr at low-speed testing and expanded the envelope. This was not something done in the past because previous helicopters could not control Nr as precisely as the 525 since the 525 has fly-by-wire and full authority digital engine control (FADEC) and because it was not required, as this is not a part of the steady operating flight envelope and analysis capabilities did not exist to predict this type of event.Regarding validating aero-servo-elastic models, Bell had data for steady-state conditions, and the models were 80 to 90% accurate for those dynamics; however, the highly dynamic flight regimes were more difficult to model. They typically modeled those by using steady-state values and adding a correlation/correction vector that was derived from flight test data.In the design phase of the Bell 525, the rotor dynamics group evaluated how the helicopter would perform at different Nr. They expected steady-state, power-off, and transient conditions and limitations. The output of this analysis provided a range of rpms that fed the limitations document used to design the helicopter. The limitations that were generated from the analysis were typically considered draft until they could be verified in flight test.The Nr operating range spanned from the minimum Nr required for lift and the maximum Nr that would overspeed the powerplant. During low airspeed flight, the maximum Nr was defined to be 103% in order to have more energy available in the rotor in the event of a single-engine failure. During high airspeed flight, the maximum Nr was 100%, and the Nr upper limit would transition to this value when flying above a specified airspeed (for example, 55 knots).Flight testing was conducted at set points for continuous flight at 103% Nr and 100% Nr, as these are the designed set points for continuous operation within the certified flight envelope. During normal operation, the helicopter's FADEC prevented Nr from drooping below these two set points with all engines operating (as long as power required was not more than the AEO power available). Continuous flight below the Nr set point could only be reached with an OEI or all-engines-inoperative (AEI) condition. The AEI case tested continuous flight down to 90% Nr. No testing of continuous rpms below 100% was conducted in any OEI condition as the maneuvers were expected to be transient in nature.The OEI maneuver resulted in reduced Nr flight within the green arc on the Nr display. Bell design team members had different understandings of whether it was expected for pilots to fly at lower Nr in the normal operating range (also known as the green arc on the Nr display):

A performance engineer specified that he expected the normal operating regime for rpm to be where you could fly within these limits continuously.

A control laws engineer considered flying at 185 knots at 90% Nr to be outside of the normal flight envelope. Tolerance would be above or below 5% of normal Nr range.

The design team did not expect to fly outside of this range. Their idea was that for certain maneuvers, it was okay to droop when there were other priorities to test. Their expectation was not to fly at 93% Nr continuously when everything was healthy.

The flight technology specialist at the time of the accident stated that the Nr green arc could mean different things to different people and was often discussed within the team. He considered 90 to 100% Nr to be transient for an AEO condition. The colors presented in the PSI were a precedent from the Bell 429 program.

There were also varying understandings of the definition of "transient." One performance engineer considered a 5-second "sustained rpm" not to be transient while other engineers considered 30 seconds to be considered steady state. The flight technology team lead said that the definition of transient was different for different people.Test pilots suggested in postaccident interviews that there could be multiple reasons why a pilot would fly at 92 to 93% when recovering from an OEI maneuver. The chase test pilot stated that flying at 92 and 93% Nr was not necessarily abnormal in an OEI condition. Further, Bell's chief test pilot provided reasons for extended flight in that rpm regime during this maneuver:

If Nr had stabilized, the pilot may not have been in a rush and could have been initiating a slow recovery that resulted in extended time at 92% Nr.

If the pilot was maneuvering the collective and felt something abnormal, the pilot instinct would be to stop moving the collective in case the abnormality originated from manipulating the collective. This could result in flight at a lower rpm.

NTSB Identification: DCA16FA19914 CFR Part 91: General AviationAccident occurred Wednesday, July 06, 2016 in Italy, TXAircraft: BELL 525, registration: N525TAInjuries: 2 Fatal.This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.On July 6, 2016, about 1148 central daylight time, an experimental Bell 525 helicopter, N525TA, broke up inflight and impacted terrain near Italy, Texas. The two pilots onboard were fatally injured and the helicopter was destroyed. The flight originated from Arlington, Texas, as a developmental flight test and was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident.